In this article on his website, conservative writer David Frum addresses a commonplace notion on the right, namely, that American's Founding Fathers were libertarians in something like the modern sense of the word (think Ron Paul).
It's certainly true that for all their political differences and their actual practices (in many cases owning slaves, for example), the Founders did generally speak highly of liberty. But as Frum correctly points out, it's a stretch to infer from this that they share, or would even recognize, the views of self-described libertarians of today.
While Frum doesn't put it quite this way, the problem is that today's libertarians view government as the chief enemy and liberty and hence equate minimum government with maximum liberty. The 1964 Civil Rights Act, for example, was an expansion of federal government power that limited the liberty of businesses to decide whom they did business with, so a lot of modern libertarians, even as they acknowledge racism as wrong, believe that the law should have constrained only government entities, not hotels or restaurants or gas stations or landlords.
In contrast, the Founders tended to view government as not inherently the enemy of individual rights but potentially, in the case of a just republic, the instrument and guarantor of those rights. (See, for example, the Declaration of Independence.) On this I'm with the Founders.
If someone constrains my liberty it makes no practical difference to me whether I'm constrained by a government or a corporation or a gang of thugs. A Ron Paul world would be much less free.